The absorption of dietary cholesterol and fat from the intestine are important modifiers of plasma cholesterol level, adiposity, and risk for atherosclerotic cardiovascular diseases. However, the genes that regulate these processes are largely unknown. We used an intercross between two inbred mouse strains, C57BL/6J and castaneus (CASA/Rk), to map a locus on chromosome 14 in linkage with plasma plant sterol levels, a surrogate measure of cholesterol absorption from the intestine. Construction and studies in a congenic strain that covers the distal end of this locus, designated 14DKK, confirmed the effect of this interval on plasma plant sterol levels and cholesterol absorption from the intestine. Moreover, further studies in 14DKK congenics disclosed that the 14DKK interval also modifies the absorption of fat and body-weight in response to high fat diet. The 14DKK interval does not harbor genes that are known to be directly involved in sterol or fat metabolism, suggesting the effect of novel genes. The main goal of this proposal is to identify these genes and clarify the mechanisms involved. This goal will be achieved through studies in two major aims. One aim will focus on testing the functional effect of candidate genes in the 14DKK interval through gene-knockdown in intestinal cell cultures. The second aim will clarify the mechanisms whereby the 14DKK interval modifies the absorption of fat from the intestine through studies on fatty acid metabolism in our congenics. Identification of causative genes in the 14DKK interval will increase our understanding on the molecular events that control the processes of cholesterol and fat absorption, may lead to the development of genetic markers to identify individuals with increased absorption of cholesterol and fat, and identify new therapeutic targets for hypercholesterolemia, overweight and obesity.